Mobile Image Format Showdown

Q: Can I restrict the test to paid traffic only?

Yes. Use URL variable targeting with UTMs to scope the experiment to paid cohorts and compare results to organic traffic.

Q: Should I also personalize by location or time of day?

After you identify a winning mobile image, layer location-based or time-based personalization to find high-performing segments such as specific cities or morning vs. evening visitors.

Q: What image dimensions should I use?

Choose dimensions that match your layout. For full-bleed mobile heroes, common ratios are 4:5, 3:4, or 1:1. Keep CTAs within safe zones and validate on popular device sizes.

Test mobile-optimized images vs. non-optimized images and prove what actually lifts conversions.

Impact

Easy

Difficulty

Medium

Time to Launch

30–60 mins

Overview of the Problem

Most teams still ship one “hero” image for every device. On mobile, that desktop-first creative becomes heavy, slow, awkwardly cropped, and CTA-unfriendly. The result: lower CTR, higher bounce, and wasted paid traffic.

Root cause

Heavy files & wrong aspect ratios → slow loads, cut-off messaging

Root cause

Same link for every device → weak attribution

Root cause

No disciplined testing → decisions by gut

Solution (Using ConversionWax)

Device-specific assets (mobile vs desktop)
Automatic image optimization
A/B testing for images
Analytics tracking (views, clicks, CTR)
URL variable targeting (UTMs)
Multi-linking personalization
Location & time layers (optional)

Step-by-Step: Implement the Solution

1 Define the test Primary KPI: Mobile CTR

Hypothesis: A mobile-optimized creative (lighter file, mobile ratio, visible CTA) will increase CTR on mobile vs. the current desktop-style image.

Guardrails: Maintain/reduce bounce; no drop in conversion rate.

2 Prepare two assets Control vs Variant

Control (Non-optimized): current desktop-designed image resized for mobile (e.g., 16:9 / 1920×1080 scaled).

Variation (Mobile-optimized):

Mobile-first ratio (4:5, 3:4, or 1:1 per layout)
CTA visible within the first 600–800px of the viewport
Crop preserves subject focus
Modern formats (WebP/AVIF) + JPEG/PNG fallbacks

3 Upload into ConversionWax Asset Library

Upload both images to Asset Library.
Name clearly: hero_control_desktopish.jpg and hero_variant_mobile.webp.

4 Target only mobile devices Device-specific assets

Restrict the test to mobile; keep desktop unchanged.

Enable Automatic image optimization to right-size files per device.

Tip: If you want “heavy vs optimized,” run that as a separate experiment.

5 Configure the A/B test 50/50 split

Control: Non-optimized image
Variation: Mobile-optimized image
Split: 50/50 (or 33/33/33 for 3 variants)
Run 1–2 weeks minimum or until significance threshold

6 Isolate traffic with URL variables UTM targeting

Add UTM tags to paid campaigns, e.g. ?utm_source=meta&utm_medium=cpc&utm_campaign=bfcm_hero_test&utm_content=variant

In URL variable targeting, scope the experiment to those UTMs to compare paid cohorts vs. organic.

7 (Optional) Add context layers Location & Time

Location-based: Compare top cities/countries.
Time-based: Morning vs evening offers.

8 Wire up links for richer attribution Multi-linking

Use unique URLs per image/device:

/offer?src=hero&v=control&m=mobile
/offer?src=hero&v=variant&m=mobile

9 QA before launch Devices & links

Expected Outcomes

+10–20% CTR on mobile hero

5–10% lower bounce on heavy imagery pages

Cleaner attribution via unique links

Insights by device/location/time

Key Takeaways

Desktop-first images are silent conversion killers on mobile.
ConversionWax makes it easy to target mobile, test variations, and prove ROI.
Use multi-linking and UTMs to connect creative to revenue, not just clicks.
Layer location/time rules to uncover outsized performance pockets.

Frequently Asked Questions

What counts as a "mobile-optimized" image?

A mobile-optimized image uses a mobile-friendly aspect ratio (e.g., 4:5, 3:4, or 1:1), has the CTA visible within the first view without scrolling, prioritizes subject focus in crop, and is exported to modern formats (WebP/AVIF) with appropriate fallbacks. ConversionWax then auto-optimizes delivery per device.

How long should I run the test?

Run until you hit sufficient sample size and confidence (commonly 95%). As a rule of thumb, 1–2 weeks with steady traffic is a good starting point. Avoid stopping early due to random spikes.

Does Automatic image optimization bias the test?

Automatic optimization equalizes file weight across variants so you measure layout and messaging, not just bytes. If you specifically want to test "heavy vs. optimized," run a separate experiment with that as the variable.

Can I restrict the test to paid traffic only?

Yes. Use URL variable targeting with your UTMs to scope the experiment to paid cohorts and compare results to organic traffic.

How do I attribute revenue back to the winning image?

Use multi-linking personalization so each variant has a unique destination URL parameter. This preserves attribution through your analytics platform, tying downstream conversions back to the exact creative and device.

Should I also personalize by location or time of day?

Often, yes. Start with the mobile image showdown. Once you have a winner, add location-based or time-based personalization to discover high-performing pockets (e.g., different cities or morning vs. evening visitors).

What image dimensions should I use?

Match your layout first. For full-bleed hero areas, common mobile ratios are 4:5, 3:4, or 1:1. Keep key content and CTAs within safe zones and verify on common device breakpoints.